Heretofore, an actinic radiation curable composition, which cures by actinic energy rays such as ultraviolet rays and electron rays, is utilized in practice for various applications such as paint, adhesives and printing ink on such as plastics, paper, woodwork and inorganic materials; a printed circuit board and electric insulation related matters. In recent years, as for actinic radiation curable ink among them, furthermore improvement of adhesion on a recording material (medium) and improvement of flexibility of cured film after curing have been desired.
Particularly, in the case of forming an image on a fiber material (medium) such as cloth by use of actinic radiation curable ink, there caused serious problems that sensation in quality of the cloth may be spoiled due to insufficient flexibility of cured film and that cured film may be peeled off when the cloth is crumpled after image formation.
On the other hand, as an ink system for ink-jet ink utilizing a polymerizing composition, there is known ultraviolet curable ink-jet ink, and this ink-jet method utilizing ultraviolet curable ink, which has been disclosed (for example refer to patent literatures 1 and 2), is attracting attention in recent years with respect to rapid drying and recording capability on a recording medium without an ink absorptive property.
However, there was a problem that cured film is broken because the formed cured film cannot follow a recording material due to lack of flexibility, resulting in printing being possible only on limited recording materials (thick ones). It has been disclosed to provide ink-jet ink with plasticity by addition of a plasticizer (for example, refer to patent literature 3). However, this is for melt type ink and there is no description with respect to ultraviolet curable ink utilizing solvent type ink.
Further, in the case of utilizing ultraviolet curable ink, there is a problem that ejection is unstable depending on working environment and particularly it becomes more severe in the case of adding a flexibility improving agent such as a plasticizer as described before.
Further, there is a problem that ink utilizing a cationic polymerizing compound is easily affected by water content (moisture) of a molecular level (for example, refer to patent literatures 4-7).
[Patent literature 1] JP-A 6-200204 (hereinafter, JP-A refers to Japanese Patent Publication Open to Public Inspection No.)
[Patent literature 2] Japanese Translation of PCT International Application Publication No. 2000-504778 (97/31071)
[Patent literature 3] JP-A 8-3493
[Patent literature 4] JP-A 2001-220526
[Patent literature 5] JP-A 2002-188025
[Patent literature 6] JP-A 2002-317139
[Patent literature 7] JP-A 2003-55449